SDL: README-migration.md: Note the GL/EGL library environment variable removals.

From 1e1442ed4ab39385dfcf1d2cafaa1300724aa9ba Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Mon, 6 Jan 2025 13:12:31 -0500
Subject: [PATCH] README-migration.md: Note the GL/EGL library environment
 variable removals.

---
 docs/README-migration.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/docs/README-migration.md b/docs/README-migration.md
index daa7af2eef16e..e3924f29ae5ce 100644
--- a/docs/README-migration.md
+++ b/docs/README-migration.md
@@ -2224,6 +2224,10 @@ The following functions have been removed:
 
 The SDL_Window id type is named SDL_WindowID
 
+The following environment variables have been removed:
+* SDL_VIDEO_GL_DRIVER - replaced with the hint SDL_HINT_OPENGL_LIBRARY
+* SDL_VIDEO_EGL_DRIVER - replaced with the hint SDL_HINT_EGL_LIBRARY
+
 The following symbols have been renamed:
 * SDL_DISPLAYEVENT_DISCONNECTED => SDL_EVENT_DISPLAY_REMOVED
 * SDL_DISPLAYEVENT_MOVED => SDL_EVENT_DISPLAY_MOVED